#if NET_4_0
// ConcurrentSkipList.cs
//
// Copyright (c) 2009 Jérémie "Garuma" Laval
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
//
//

using System;
using System.Threading;
using System.Collections;
using System.Collections.Generic;
using System.Runtime.Serialization;

namespace System.Collections.Concurrent
{
	public class ConcurrentDictionary<TKey, TValue> : IDictionary<TKey, TValue>,
	  ICollection<KeyValuePair<TKey, TValue>>, IEnumerable<KeyValuePair<TKey, TValue>>,
	  IDictionary, ICollection, IEnumerable
	{
		class Pair
		{
			public readonly TKey Key;
			public TValue Value;

			public Pair (TKey key, TValue value)
			{
				Key = key;
				Value = value;
			}

			public override bool Equals (object obj)
			{
				Pair rhs = obj as Pair;
				return rhs == null ? false : Key.Equals (rhs.Key) && Value.Equals (rhs.Value);
			}

			public override int GetHashCode ()
			{
				return Key.GetHashCode ();
			}
		}

		class Basket: List<Pair>
		{
			public SpinLock Lock = new SpinLock (true);
		}

		// Assumption: a List<T> is never empty
		ConcurrentSkipList<Basket> container
			= new ConcurrentSkipList<Basket> ((value) => value[0].GetHashCode ());
		int count;
		IEqualityComparer<TKey> comparer;

		public ConcurrentDictionary () : this (EqualityComparer<TKey>.Default)
		{
		}

		public ConcurrentDictionary (IEnumerable<KeyValuePair<TKey, TValue>> values)
			: this (values, EqualityComparer<TKey>.Default)
		{
			foreach (KeyValuePair<TKey, TValue> pair in values)
				Add (pair.Key, pair.Value);
		}

		public ConcurrentDictionary (IEqualityComparer<TKey> comparer)
		{
			this.comparer = comparer;
		}

		public ConcurrentDictionary (IEnumerable<KeyValuePair<TKey, TValue>> values, IEqualityComparer<TKey> comparer)
			: this (comparer)
		{
			foreach (KeyValuePair<TKey, TValue> pair in values)
				Add (pair.Key, pair.Value);
		}

		// Parameters unused
		public ConcurrentDictionary (int concurrencyLevel, int capacity)
			: this (EqualityComparer<TKey>.Default)
		{

		}

		public ConcurrentDictionary (int concurrencyLevel,
		                             IEnumerable<KeyValuePair<TKey, TValue>> values,
		                             IEqualityComparer<TKey> comparer)
			: this (values, comparer)
		{

		}

		// Parameters unused
		public ConcurrentDictionary (int concurrencyLevel, int capacity, IEqualityComparer<TKey> comparer)
			: this (comparer)
		{

		}

		void Add (TKey key, TValue value)
		{
			while (!TryAdd (key, value));
		}

		void IDictionary<TKey, TValue>.Add (TKey key, TValue value)
		{
			Add (key, value);
		}

		public bool TryAdd (TKey key, TValue value)
		{
			Basket basket;
			bool taken = false;

			// Add a value to an existing basket
			if (TryGetBasket (key, out basket)) {
				try {
					basket.Lock.Enter (ref taken);

					foreach (var p in basket) {
						if (comparer.Equals (p.Key, key))
							return false;
					}
					basket.Add (new Pair (key, value));
				} finally {
					if (taken)
						basket.Lock.Exit ();
				}
			} else {
				// Add a new basket
				basket = new Basket ();
				basket.Add (new Pair (key, value));

				if (container.TryAdd (basket)) {
					Interlocked.Increment (ref count);
					return true;
				} else {
					return false;
				}
			}

			Interlocked.Increment (ref count);

			return true;
		}

		void ICollection<KeyValuePair<TKey,TValue>>.Add (KeyValuePair<TKey, TValue> pair)
		{
			Add (pair.Key, pair.Value);
		}

		public TValue AddOrUpdate (TKey key, Func<TKey, TValue> addValueFactory, Func<TKey, TValue, TValue> updateValueFactory)
		{
			Basket basket;
			TValue temp = default (TValue);
			bool taken = false;

			if (!TryGetBasket (key, out basket)) {
				Add (key, (temp = addValueFactory (key)));
			} else {
				try {
					basket.Lock.Enter (ref taken);

					Pair pair = basket.Find ((p) => comparer.Equals (p.Key, key));
					if (pair == null)
						throw new InvalidOperationException ("pair is null, shouldn't be");
					pair.Value = (temp = updateValueFactory (key, pair.Value));
				} finally {
					if (taken)
						basket.Lock.Exit ();
				}
			}

			return temp;
		}

		public TValue AddOrUpdate (TKey key, TValue addValue, Func<TKey, TValue, TValue> updateValueFactory)
		{
			return AddOrUpdate (key, (_) => addValue, updateValueFactory);
		}

		TValue GetValue (TKey key)
		{
			TValue temp;
			if (!TryGetValue (key, out temp))
				// TODO: find a correct Exception
				throw new ArgumentException ("Not a valid key for this dictionary", "key");
			return temp;
		}

		public bool TryGetValue (TKey key, out TValue value)
		{
			Basket basket;
			value = default (TValue);
			bool taken = false;

			if (!TryGetBasket (key, out basket))
				return false;

			try {
				basket.Lock.Enter (ref taken);

				Pair pair = basket.Find ((p) => comparer.Equals (p.Key, key));
				if (pair == null)
					return false;
				value = pair.Value;
			} finally {
				if (taken)
					basket.Lock.Exit ();
			}

			return true;
		}

		public bool TryUpdate (TKey key, TValue newValue, TValue comparand)
		{
			Basket basket;
			bool taken = false;

			if (!TryGetBasket (key, out basket))
				return false;

			try {
				basket.Lock.Enter (ref taken);

				Pair pair = basket.Find ((p) => comparer.Equals (p.Key, key));
				if (pair.Value.Equals (comparand)) {
					pair.Value = newValue;

					return true;
				}
			} finally {
				if (taken)
					basket.Lock.Exit ();
			}

			return false;
		}

		public TValue this[TKey key] {
			get {
				return GetValue (key);
			}
			set {
				Basket basket;
				bool taken = false;

				if (!TryGetBasket (key, out basket)) {
					Add (key, value);
					return;
				}

				try {
					basket.Lock.Enter (ref taken);

					Pair pair = basket.Find ((p) => comparer.Equals (p.Key, key));
					if (pair == null)
						throw new InvalidOperationException ("pair is null, shouldn't be");
					pair.Value = value;
				} finally {
					if (taken)
						basket.Lock.Exit ();
				}
			}
		}

		public TValue GetOrAdd (TKey key, Func<TKey, TValue> valueFactory)
		{
			Basket basket;
			TValue temp = default (TValue);

			if (TryGetBasket (key, out basket)) {
				Pair pair = null;
				bool taken = false;

				try {
					basket.Lock.Enter (ref taken);

					pair = basket.Find ((p) => comparer.Equals (p.Key, key));
					if (pair != null)
						temp = pair.Value;
				} finally {
					if (taken)
						basket.Lock.Exit ();
				}

				if (pair == null)
					Add (key, (temp = valueFactory (key)));
			} else {
				Add (key, (temp = valueFactory (key)));
			}

			return temp;
		}

		public TValue GetOrAdd (TKey key, TValue value)
		{
			return GetOrAdd (key, (_) => value);
		}

		public bool TryRemove(TKey key, out TValue value)
		{
			value = default (TValue);
			Basket b;
			bool taken = false;

			if (!TryGetBasket (key, out b))
				return false;

			try {
				b.Lock.Enter (ref taken);

				TValue temp = default (TValue);
				// Should always be == 1 but who know
				bool result = b.RemoveAll ((p) => {
					bool r = comparer.Equals (p.Key, key);
					if (r) temp = p.Value;
					return r;
				}) >= 1;
				value = temp;

				if (result)
					Interlocked.Decrement (ref count);

				return result;
			} finally {
				if (taken)
					b.Lock.Exit ();
			}

			return false;
		}

		bool Remove (TKey key)
		{
			TValue dummy;

			return TryRemove (key, out dummy);
		}

		bool IDictionary<TKey, TValue>.Remove (TKey key)
		{
			return Remove (key);
		}

		bool ICollection<KeyValuePair<TKey,TValue>>.Remove (KeyValuePair<TKey,TValue> pair)
		{
			return Remove (pair.Key);
		}

		public bool ContainsKey (TKey key)
		{
			return container.ContainsFromHash (key.GetHashCode ());
		}

		bool IDictionary.Contains (object key)
		{
			if (!(key is TKey))
				return false;

			return ContainsKey ((TKey)key);
		}

		void IDictionary.Remove (object key)
		{
			if (!(key is TKey))
				return;

			Remove ((TKey)key);
		}

		object IDictionary.this [object key]
		{
			get {
				if (!(key is TKey))
					throw new ArgumentException ("key isn't of correct type", "key");

				return this[(TKey)key];
			}
			set {
				if (!(key is TKey) || !(value is TValue))
					throw new ArgumentException ("key or value aren't of correct type");

				this[(TKey)key] = (TValue)value;
			}
		}

		void IDictionary.Add (object key, object value)
		{
			if (!(key is TKey) || !(value is TValue))
				throw new ArgumentException ("key or value aren't of correct type");

			Add ((TKey)key, (TValue)value);
		}

		bool ICollection<KeyValuePair<TKey,TValue>>.Contains (KeyValuePair<TKey, TValue> pair)
		{
			return ContainsKey (pair.Key);
		}

		public KeyValuePair<TKey,TValue>[] ToArray ()
		{
			// This is most certainly not optimum but there is
			// not a lot of possibilities

			return new List<KeyValuePair<TKey,TValue>> (this).ToArray ();
		}

		public void Clear()
		{
			// Pronk
			container = new ConcurrentSkipList<Basket> ((value) => value [0].GetHashCode ());
		}

		public int Count {
			get {
				return count;
			}
		}

		public bool IsEmpty {
			get {
				return count == 0;
			}
		}

		bool ICollection<KeyValuePair<TKey, TValue>>.IsReadOnly {
			get {
				return false;
			}
		}

		bool IDictionary.IsReadOnly {
			get {
				return false;
			}
		}

		public ICollection<TKey> Keys {
			get {
				return GetPart<TKey> ((kvp) => kvp.Key);
			}
		}

		public ICollection<TValue> Values {
			get {
				return GetPart<TValue> ((kvp) => kvp.Value);
			}
		}

		ICollection IDictionary.Keys {
			get {
				return (ICollection)Keys;
			}
		}

		ICollection IDictionary.Values {
			get {
				return (ICollection)Values;
			}
		}

		ICollection<T> GetPart<T> (Func<KeyValuePair<TKey, TValue>, T> extractor)
		{
			List<T> temp = new List<T> ();

			foreach (KeyValuePair<TKey, TValue> kvp in this)
				temp.Add (extractor (kvp));

			return temp.AsReadOnly ();
		}

		void ICollection.CopyTo (Array array, int startIndex)
		{
			KeyValuePair<TKey, TValue>[] arr = array as KeyValuePair<TKey, TValue>[];
			if (arr == null)
				return;

			CopyTo (arr, startIndex, count);
		}

		void CopyTo (KeyValuePair<TKey, TValue>[] array, int startIndex)
		{
			CopyTo (array, startIndex, count);
		}

		void ICollection<KeyValuePair<TKey, TValue>>.CopyTo (KeyValuePair<TKey, TValue>[] array, int startIndex)
		{
			CopyTo (array, startIndex);
		}

		void CopyTo (KeyValuePair<TKey, TValue>[] array, int startIndex, int num)
		{
			// TODO: This is quite unsafe as the count value will likely change during
			// the copying. Watchout for IndexOutOfRange thingies
			if (array.Length <= count + startIndex)
				throw new InvalidOperationException ("The array isn't big enough");

			int i = startIndex;

			foreach (Basket b in container) {
				bool taken = false;

				try {
					b.Lock.Enter (ref taken);

					foreach (Pair p in b) {
						if (i >= num)
							break;
						array[i++] = new KeyValuePair<TKey, TValue> (p.Key, p.Value);
					}
				} finally {
					if (taken)
						b.Lock.Exit ();
				}
			}
		}

		public IEnumerator<KeyValuePair<TKey, TValue>> GetEnumerator ()
		{
			return GetEnumeratorInternal ();
		}

		IEnumerator IEnumerable.GetEnumerator ()
		{
			return (IEnumerator)GetEnumeratorInternal ();
		}

		IEnumerator<KeyValuePair<TKey, TValue>> GetEnumeratorInternal ()
		{
			foreach (Basket b in container) {
				bool taken = false;

				try {
					b.Lock.Enter (ref taken);

					foreach (Pair p in b)
						yield return new KeyValuePair<TKey, TValue> (p.Key, p.Value);
				} finally {
					if (taken)
						b.Lock.Exit ();
				}
			}
		}

		IDictionaryEnumerator IDictionary.GetEnumerator ()
		{
			return new ConcurrentDictionaryEnumerator (GetEnumeratorInternal ());
		}

		class ConcurrentDictionaryEnumerator : IDictionaryEnumerator
		{
			IEnumerator<KeyValuePair<TKey, TValue>> internalEnum;

			public ConcurrentDictionaryEnumerator (IEnumerator<KeyValuePair<TKey, TValue>> internalEnum)
			{
				this.internalEnum = internalEnum;
			}

			public bool MoveNext ()
			{
				return internalEnum.MoveNext ();
			}

			public void Reset ()
			{
				internalEnum.Reset ();
			}

			public object Current {
				get {
					return Entry;
				}
			}

			public DictionaryEntry Entry {
				get {
					KeyValuePair<TKey, TValue> current = internalEnum.Current;
					return new DictionaryEntry (current.Key, current.Value);
				}
			}

			public object Key {
				get {
					return internalEnum.Current.Key;
				}
			}

			public object Value {
				get {
					return internalEnum.Current.Value;
				}
			}
		}

		object ICollection.SyncRoot {
			get {
				return this;
			}
		}


		bool IDictionary.IsFixedSize {
			get {
				return false;
			}
		}

		bool ICollection.IsSynchronized {
			get { return true; }
		}

		bool TryGetBasket (TKey key, out Basket basket)
		{
			basket = null;
			if (!container.GetFromHash (key.GetHashCode (), out basket))
				return false;

			return true;
		}
	}
}
#endif